Cyber attacks on US weapons programs and manufacturers are a "pervasive" problem that requires greater attention, the top US arms buyer said on Thursday, saying that he would add cyber-security to the Pentagon's guidelines for buying weapons.

President Barack Obama asked tech industry executives on Friday for closer cooperation in defending against hackers after high-profile attacks against companies like Sony that exposed weaknesses in America's cyber defenses.

North Korea may be facing explosive hacking accusations, but analysts are questioning how an isolated, impoverished country with limited Internet access could wage cyber sabotage -- and many experts believe China plays a role.